Kristen Stewart Flaunts Cleavage in Plunging Red Gown

Although she doesn't star in the upcoming sex-and-violence filled Cosmopolis alongside her beau Robert Pattinson, Kristen Stewart certainly stole the show at the premiere's red carpet.

In Cannes, France on Friday, the Snow White and the Huntsman actress, 22, got decked out in support of her actor boyfriend and flaunted her assets in an extremely low-cut, cleavage baring Reem Acra gown.

She complemented her look with a matching red lipstick and wore her hair up, which showed off the dress' sheer, lace back.

At the event, Stewart worked her sexy red ensemble alongside Pattinson's BFF and her On the Road costar, Tom Sturridge. Absent from the red carpet: Sturridge's pregnant fiancee Sienna Miller, who is expecting the couple's first child this year.

"They looked really comfortable, sitting closely and chatting," an onlooker tells Us Weekly about the Twilight Saga costars. "He was talking to her and not paying attention to anyone else. Every now and then she would laugh and he would smile at her."